Magnetic Negative Stiffness Mechanism for Low-Frequency Vibration Isolation
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Solution Overview
Problem
Existing quasi-zero stiffness vibration isolators face challenges in achieving a balance between vibration isolation bandwidth and bearing capacity, particularly in low-frequency applications, due to sensitivity to stiffness and load changes, and require adjustments to maintain optimal performance.
Innovation Solution
A negative stiffness generating mechanism with a compact structure, comprising an inner-ring magnet group, an outer-ring magnet group, and a supporting shaft, allows for adjustable negative stiffness through a negative stiffness adjusting device, ensuring the vibration isolator remains at an ideal balance position with dynamic stiffness close to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the stiffness of the system is reduced to expand vibration isolation bandwidth, then the vibration isolation bandwidth is improved, but the bearing capacity is reduced
Solution Approach 1:
The patent employs parameter changes by introducing a negative stiffness mechanism that can dynamically adjust the system's stiffness parameter. Through the adjustable negative stiffness mechanism, the system achieves low dynamic stiffness for vibration isolation while maintaining high static stiffness for bearing capacity, effectively resolving the contradiction between vibration isolation bandwidth and bearing capacity
Solution Approach 2:
The patent uses a composite structure combining positive stiffness springs and negative stiffness mechanisms. This composite system allows the positive stiffness component to provide bearing capacity while the negative stiffness component reduces dynamic stiffness, achieving both high bearing capacity and wide vibration isolation bandwidth simultaneously
2Length of moving object
If the mass of the system is increased to expand vibration isolation bandwidth, then the vibration isolation bandwidth is improved, but the static deformation is increased
Solution Approach 1:
Instead of increasing mass to reduce natural frequency, the patent changes the stiffness parameter by introducing negative stiffness. This approach reduces dynamic stiffness to expand vibration isolation bandwidth while keeping the static deformation small because the negative stiffness mechanism only activates during dynamic vibration, not under static load
3Force
If the stiffness of the system is increased to improve bearing capacity in limited space, then the bearing capacity is improved, but the inherent frequency is improved and the vibration isolation frequency band is reduced
Solution Approach 1:
The patent applies parameter changes by using an adjustable negative stiffness mechanism that can switch between different stiffness states. Under static conditions, the system maintains high stiffness for bearing capacity. During vibration, the negative stiffness mechanism activates to reduce dynamic stiffness, thereby expanding the vibration isolation frequency band while preserving bearing capacity
4Force
If pre-compression horizontal spring type or buckling beam type negative stiffness mechanisms are used, then the negative stiffness is generated, but the transverse size is large
Solution Approach 1:
The patent applies the nesting principle by placing the negative stiffness mechanism inside the cylindrical space formed by the positive stiffness springs. The negative stiffness mechanism is nested within the same transverse footprint as the positive stiffness springs, achieving compact integration without increasing transverse size
Solution Approach 2:
The patent transitions from horizontal/transverse arrangement to vertical/axial arrangement. Instead of arranging negative stiffness elements perpendicular to the springs (which increases transverse size), the patent arranges them coaxially along the vertical axis, utilizing the axial dimension to achieve compact structure
5Area of stationary object
If permanent magnet type or electromagnetic type negative stiffness mechanisms are used, then the structure is compact and non-contact, but the negative stiffness magnitude is limited
Solution Approach 1:
The patent merges multiple negative stiffness mechanisms (pre-compression springs, buckling beams, and magnetic components) into a unified system. This combination allows the mechanical components to provide large negative stiffness magnitude while the magnetic components provide non-contact force transmission and compact structure, achieving both large negative stiffness and compact design
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The mechanism effectively adapts to variations in positive stiffness and load, maintaining the vibration isolator at an ideal balance position with dynamic stiffness near zero, thereby enhancing vibration isolation performance and robustness.
Implementation Method 1
Force conduction is carried out through magnetic field interaction, and the structure belongs to a non-contact negative stiffness structure
Implementation Method 2
The upper movable magnetic ring and the lower movable magnetic ring are symmetrically arranged relative to the center of the axial height of the inner fixed magnetic ring
Data Source
AI summary
A negative stiffness generating mechanism and a quasi-zero stiffness vibration isolator are provided. A housing is mounted on a base, and the axial relative positions of the housing and the base can be adjusted; a negative stiffness unit comprises inner-ring magnets, outer-ring magnets and a supporting shaft, the supporting shaft axially slides on the base and passes through the housing, the inner-ring magnets fixedly sleeve the supporting shaft, and the outer-ring magnets sleeve outside the inner-ring magnets and are divided into upper and lower groups of outer-ring magnets; the upper and lower groups of outer-ring magnets can synchronously move through a negative stiffness adjusting device; and the axial relative positions of the middle planes of the outer-ring and inner-ring magnets can be adjusted by adjusting the axial relative positions of the housing and the base. The isolator comprises a negative stiffness generating mechanism and a positive stiffness unit.